Fluid measurement systems may be used to measure a flow rate or volume of a fluid or gas. For example, dispensing systems may use feedback from a positive displacement fluid meter to control the volume of fluid dispensed. Such control systems are often used in lieu of time-on controls to more accurately dispense precise amounts of fluid or gas and are commonly used in a variety of settings including, but not limited to, the industrial, healthcare, pharmaceutical and food and beverage industries. For example, a flow meter may be used in the manufacturing process of a drug which requires accurate measurement of two materials to be mixed into a single batch. The flow meter may be installed in the supply lines of the respective materials and feedback from the meters may be used to dispense the appropriate amount of each material into a blend tank to be mixed. Flow meters may measure accurately measures a volume of fluid or gas to comply with regulatory requirements in many industries.
Oval gear meters are an example of a positive displacement flow meter. Such positive displacement flow meters generally involve mechanical displacement of components (e.g., gears) of the flow meter to measure flow. An oval gear meter provides a pair of intermeshing oval gears positioned within a chamber. A fluid may be introduced into the chamber through an inlet, and the pair of gears may rotate synchronously with each other. The intermeshing of the gears prevents the fluid from passing between the gears. Rather, the fluid passes around the gears within pockets defined between the oval gears and the chamber. The volume of each pocket of fluid is precisely measured. Thus, the volume of fluid exiting the chamber during each rotation is known. Thus, measuring the number of rotations of the gears can be used to determine the volume of fluid, and the speed of rotation of the gears can be used to determine the flow rate.
Typical oval gear meters may accurately measure fluid flow in applications having a high fluid flow rate or a relatively uniform fluid flow (e.g., flow through peristaltic pumps or in pressure-maintained fluid lines). In applications having low flow rates or where the flow is non-uniform, however, typical oval gear meters may have a lower accuracy of measurement. For example, non-uniform flow generated by a diaphragm pump may cause pressure shocks which generate oscillations in the fluid lines after each pump cycle. The oscillations may produce vibrations, or “jitter,” of the oval gears, or a backflow of fluid through the oval gear meter. Such jitters or backflow may induce false signals and/or an inaccurate rotational count of the oval gear meter. False signals may also be induced by backflow of fluid into an oval gear meter. Additionally, oval gear meters in low flow applications may also have increased error due to leakage of fluid around the oval gears.
Check valves are well-known in the art for regulating flow. However, adding one or more check valves may increase the cost and complexity of the flow measuring system.